Shock absorber



Nov. 18, 1930. L. w.y GREVE 1,782,141

Y SHOCK ABSORBER l Voriginar Filed April so, `192e 2 Sheets-sheet i Nov. 1s, 1930. L w GREVE 1,782,141

sHocK ABSORBER OriginalA Filed'April 30, 1928 2 Sheets-Sheet 2 Patented Nov. 18., 1.93

UNITED ASTATI-:s

PATENT OFFICE LOUIS TILLIAMI GREVE, OF'CLEVELAND, OHIO", ASSIGNOR T0 THE CLEVELAND PNEU- MATIC TOOL COMPANY, F CLEVELAND, OHIO, A CORPORATION OF OHIO snocx ABsoRBEn p.

Original application filed April 30, '1928, Serial-No. 273,929. Divided and this application led July 26,

` 1929.1Serial No. 381,178.

This invention-relates to improvements in- -shock absorbers for air craft, "particularly amphibians, being a division -of my copending application, Serial No. 273,929, filed April 30, 1928.J In air craft of this class the landing gear must be retracted at times when the plane is alighting upon the water. Otherwise the landing gear would be torn loose from the ship, because of the resistance -Npoifered by the relatively unyielding water -v through which the landing gear would have to pass rapidly. Consequently it is the general practice to mount the forward ground wheels` upon movable frames or systems of links and levers and to arrange for their operation usually from the pilots cockpit in order that the Ylanding gear may be quickly and easily lowered into operative position or retracted whenever the occasion therefor arises.

This necessary movability -of the landing gear and the relatively short pivotally mounted elements of the same which are employed to accomplish'movability have rendered it diflicult, if not impossible, to incorporate in the landing gear satisfactory shock absorbing means of the types lin use upon airplanes, and as a resultamphibians heretofore have generally been without effi- 3o cient shock absorbing equipment, which'obviously is detrimental to"the rather delicate structure of such craft and a source of discomfort to the ilot and passengers.

One of the obJects of the present invention,

. therefore, is the provision of eflicient shock absorbing equipment. for the retractable landing gear of amphibians.

Another object is the provision of a fluid shockl absorber, to be employed in the land- 4o ing gear of an amphibian as a part thereof,

which ordinarily occupies` a substantiallyv horizontal position.

' Another object is the provision of a com- -bined liquid and air strut so designed. and arranged that it will function properly and efficiently in a substantially horizontalfposition. Another object is the provision of an air dome extending laterally'4 from the cylinder of the shock absorber in a generally vertical 5o direction, and so connected to the interior of the cylinder that in none of the positions ass umed by the shock absorber in moving fromv `operative to inoperative position and vice versa will air escape from the dome into the cylinder.

Other objects' and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawings, in which,

p Figure 1 is a transverse sectional view extending approximately half way through the hull of an amphibian and illustrating a landinggear embodying my invention, said gear fbeing in retracted position.

Fig. 2 is a similar view of the other half I of the hull, with the corresponding portion of the'landinggear shown in full lines in its operative position and in dotted lines in its aisorber strut with at 10 and the curved `upper surface at 11, the Y hull on each side of the center being provided with a wall 12-for the reception ofa portion of the Wheel 13 of the landing gear when the latter is in its retracted position. The surfaces 11 of theV hull are necessarily interrupted or cut into further for the accommodation of the bracing and retracting linkage presently to be described.

The wheels 13 are' mounted for rotation upon axles 14v which are preferably bent substantially as shown in the drawings and attached at their inner ends by pivots 15 to the hull or its framework. A link 16is also mounted upon the pivot 15 and at its other end is connected by a pivot 17 with one extremityof a link 18, the other extremity of which may, and preferably does compriseV a cylinder element 24 and a rpiston element 25. In order to accomplish the movement of the landing gear from operative position to retracted position and' pvice versa, anysuitable means may be provided for swinging thelink 22 upon the pivot 21. This is preferably accomplished, however, by providing the link 22 beyond the pivot 21 with a sector 26,

the teeth of which mesh'with `a spiral gear 27, the two 'gears' 27 `being keyed upon a shaft 28 that Amay be rotated by any suitable means, notshown, such means being operable preferably from the'pilot-s cockpit.

, Referring now to Figs. 3-and"4, wherein the detailed construction of thexshock absorber is illustrated, it will be observed that the cylinder element 24 is provided upon its upper side near its closed end with an integral annular upwardly' extending exterior-ly threaded cup 29. This cup 29 has threadably lmounted thereon a dome 30, the cup and dome together enclosing a chamber which is in communication with the cylinder near the of the gland there is a 39, which normally rests against the shoulder' closed end thereof by means of open ports 31 'and 32. The dome is provided with an oil filler opening closed by a threaded plug 33 and with an air construction.

The cylinder element 24 .at its open end is provided with an enlargement 35 for the v reception of packing 36 which surrounds the skirt 37 of the piston element 25. Into the valve 34 of any usual endof the enlargement 35 there is threaded a packing gland nut 38. At the opposite end packing retainer ring i 40 formed betweenthe cylinder 24 and its enlargement 35. This` ring 39 may move away from the shoulder 40 to some extent 1n response to pressure communicated vto'v it from the space within the cylinder beyond the pressure is 'heavy and to permit it to the piston head 41 by way of passages 42 and 43 throughthepiston head and ports 44 through a valve ring 45. vBy this means the packing 3ft/may' be automaticallycompressed'moreor less tomake it tight when loosen up when the pressure is relieved somewhat. This automatic regulation of the packing is disclosed more in detail in an application filed December 9, 1927 by John F. Wallace, Serial No. 238,838. l

.The head of the cylinder element 24 has a mounting 1ug 46 integral-therewith, and

asimilar lug 47 is' provided at the outer endof piston element 25, Ithese lugs being provided with openings for the reception lof pivots 23 and 17,` respectively. i

Whenv the landing gear is in operative position and the machine is making a landing or when it is taxiing over the grou-pd, the cylinder and' piston 24, 25 together -constitute a'strut, in other words, they perform the usual function of a shock absorber. When the landing gear is being retracted, however, these two parts together constitute a tension element. At such times the head 41 of the piston presses through valve ring against packing retainer ring39, whereby the extension of the parts is stopped or lim1ted.

Each of the* passages 42 has a restriction 42 therein.4 The ring. 45 is loosely mounted so as to float in the space between the" overhanging portion of the piston head and thel shoulder formed at the inner end of the piston skirt 37, the ports 44 in: the ring being positioned to registerfwith the passages 42 when the ring is in the .position illustrated in Figs. '3 and 6. When the ring 45 is in the position of` Fig.' 5 the unrestricted Vpassages 43 are open.. When it isin the position of Fig. 6, however, these passages are closed.

The mounting of the shock absorber is, of course, such that the dome 30 extendsl above the cylinder 24. The plug 33 is removed andA suicient oil or other liquid is poured into the filler hole to entirely fill the space within the cylinder and extend u iIfto the dome to about the level illustrated 1n Fig. 3, when the piston is extended as far as itwill go, that is,

when it is. in the position illustrated inFig. 3. 'Air is then pumped into thedome through r the air valve 34 until the desired pressure is reached. This air is trapped in the dome Where it acts upon the surfaceof the liquid, and a considerable amount ofjtilting of the shock absorber upon its 'mountings may occur without cylinder 24. lt is relatively easy to maintain substantially oil tight -sliding surfaces between the cylinder and piston, but quite diliicult to make such joints tight against the escape of compressed air.` tioned the ports 31, 32, however, that `when the piston end of the shock vated, so that air would tend toA collect at the sliding surfaces, the oil aboveports 31, 32 is relatively deep. Consequently there is littley opportunityv for air to escape from the dome 30 and pass through ports 31, 32 into the cylinder, even though the oil washes about considerably due to shocks transmitted from the ground wheels.

Operation-#Assuming that the landing` gear isin operativeposition, as shown in Fig. 2 and that the plane is on the ground, the Weight of the plane is transmitted to the ground wheels v13 through the shock absorbers, and consequently the pistons 41 are advanced in the cylinders 24 to such an extent permitting any air to get into theV absorber is ele-v I have so posithat the compression of the air in the domes 30 balances the weight of the plane. Now when the plane takes olf and its weight is rev moved from the struts, the pressure in the A in the high'l domes 30 expands the struts to the liinit, that is until the pistons` 41 engage the retainer rings 39 through the intermediacy of thevalve rings 45. By this means the rings 39 are moved sli htly, thereby expanding the packing 36. tight seal is thus formed between the two telescoping members 24 and 25 when the plane is in the air.

When a landing is made the landing gear strikesthe ground with considerable force. This force causes the piston head 41 in each strut tomove inwardly in the cylinder 24, and this movement is transmitted by the oil into the dome 30, where it acts to compress the airg therein. Durin this stroke the ring 45 is in the position of ig. 5, and a minimum resistance is offered to the flow of oil through passages 43 and 42 and through the ports 44 l'ntol the annular space 50 behind the piston Wheh the force of the impact is balanced bythe pressure built up in the dome 30, the' piston stops and the energy thus stored up y compressed air in the dome tends to r1ve the piston outwardly with ak violent motion. The piston head immediately catches up with'. the loose valve ring 45, as indicated in. Fig. 6, and the latter is held in this position by thepressure of the oil Abehind it. Consequently the'passages 43 are closed and the oil from the annular passage is permitted to flow out past the piston head only so fast as it can be metered through the restrictions 42 in the passages 42. The rebound is thus slowed up. At the same time, however, the oil in the annular space' 30 is put under heav pressure, and this pressure is communicate to the' retainer ring 39, moving the latter outwardly and compressing the the cylinder in the expanded position of the strut, and containing also a quantity of c0111-,

pressed air, said piston behind the piston head being shaped to provide an annular chamber between the piston and cylinder, and means for permitting-relatively free iow of liquid intosaid annular chamber upon the forward stroke of the piston and restricted flow out .of said chamber' when the piston moves in the opposite direction.

2. In a shock absorbingstrut for aircraft, a cylinder, a piston therefor, means for mounting said cylinder and piston to have a substantiall horizontal operative position,

. a -dome exten ing upwardly from said cylin der in thel operative position of the latter,

said dome being in communication with the f cylinder near the closed end thereof beyond the innermost position of 'the cient'to ll a portion of the dome and all of the cylinder in the expanded position of the strut, said piston behind the piston head In testimony whereof; I hereunto affix my' Y signature. y l

LOUIS WILLIAM GREVE.

packing 36, whereby mcrcased friction assists in slowingup the rebound action.

While I have illustrated and described the invention in considerable detail, such detail disclosure has been resortedto primarily for illustrative purposes, and is not to be construed as limiting the invention except as it may be included specifically in the appended claims.

Having thus fully described my invention,"

the innermost position of the piston, said strut containing a quantity of liquid sufli- 'cient to fill a'portonV of the dome and all of iston, said -1 strut containing a quantity of iquid sui.

i iso 

